A person completes 80km of a journey at 10km/h and the remaining 70km in 7hours. His average speed for the whole journey is:
- A10.5 km/h
- B9 km/h
- C10 km/h
- D9.5 km/h
Solution & Step-by-step Explanation
The formula for average speed is:
Average Speed=
Total Time
Total Distance
Step 1: Calculate total distance
Total Distance=80km+70km=150km
Step 2: Calculate total time
Time taken for the first part =
Speed
Distance
=
10
80
=8hours
Time taken for the second part =7hours
Total Time=8+7=15hours
Step 3: Calculate average speed
Average Speed=
15
150
=10km/h
Average Speed=
Total Time
Total Distance
Step 1: Calculate total distance
Total Distance=80km+70km=150km
Step 2: Calculate total time
Time taken for the first part =
Speed
Distance
=
10
80
=8hours
Time taken for the second part =7hours
Total Time=8+7=15hours
Step 3: Calculate average speed
Average Speed=
15
150
=10km/h